In the magnetic recording method, a magnetic bit is seriously affected by the external temperature and other factors as the recording density is increased. This requires use of a recording medium having a high coercive force. However, use of such a recording medium increases the magnetic field required for recording. The upper limit of the magnetic field generated by a recording head is determined by the saturated magnetic flux density. The value thereof is already close to the limit of each material, and a drastic increase in this value cannot be expected. In one of the techniques proposed to solve this problem, magnetic weakening is caused by local heating at the time of recording, and recording is performed when the coercive force is reduced. After that, heating is suspended and natural cooling is started, whereby the stability of the recorded magnetic bit is ensured. This method is known under the name of the thermally assisted magnetic recording method.
However, in this recording method, part of a magnetic disk is heated using a heating section, and the coercive force in this region is reduced. A magnetic pattern is formed in the region with reduced coercive force using a recording element. A series of these operations is performed to reduce the required generation magnetic field of the recording element. Further, subsequent to the recording operation, the disk temperature is reduced back to the room temperature, and therefore, even a small magnetic pattern is less subjected to thermal agitation. A stable recording pattern is maintained for a long time. Achievement of this advantage is what is intended by this thermal assisted magnetic recording method, wherein a magnetic pattern is formed in the region of the magnetic field generated by the recording element.
However, in a magnetic recording device using this thermally assisted magnetic recording head, when the thermally assisted magnetic recording head is moved along an arc in the radial direction of the magnetic disk, there will be a change in the angle between the track recorded by the recording element, and the head. Then the heating section located far away forwardly of the recording element may heat a different track. In such a case, the track wherein the recording element passes by is not heated, and a magnetic pattern cannot be formed correctly on the magnetic disk.
To solve such a problem, for example, a laser beam used for heating is applied from the direction as viewed obliquely from the region of the generated magnetic field, so as to bring the heated region closer to the region of generated magnetic field (Patent Document 1). In another method having been proposed, a laser beam for heating is applied from the position closest to the head wherever possible, using a waveguide (Patent Document 2).
According to the method disclosed in Patent Document 1, however, if the distance between the head and magnetic disk is reduced to ensure high-density magnetic recording, the effect of applying a laser beam in a slanting direction will be reduced, and the position immediately below the recording element cannot be heated. According to the method disclosed in Patent Document 2, if the size of the recording element is reduced to ensure high-density magnetic recording, the formation of the waveguide will be very difficult.
In still another method, an offset mechanism is provided to move the region heated by the heating section, across the width of the slider relative to the recording element, thereby overcoming the disadvantage of the heating section being located separately from the recording element, and ensuring high-density recording (Patent Document 3). The Patent Document 3 also discloses the method of providing a plurality of recording elements and heating sections, wherein one of the recording elements or one of the heating sections is selected as appropriate so that the region heated by the recording element and heating section will be moved relatively across the width of the head slider.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-319387
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2002-50012
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2004-134051